Enhanced conversion efficiency of InGaN multiple quantum well solar cells grown on a patterned sapphire substrate

This study demonstrated the enhanced conversion efficiency of an indium gallium nitride (InGaN) multiple quantum well (MQW) solar cell fabricated on a patterned sapphire substrate (PSS). Compared to conventional solar cells grown on a planar sapphire substrate, threading dislocation defects were found to be reduced from 1.28 x 10(9) to 3.62 x 10(8) cm(-2), leading to an increase in short-circuit current density (J(SC) = 1.09 mA.cm(-2)) of approximately 60%. In addition, the open-circuit voltage and fill factor (V-OC = 2.05 V; FF = 51%) of the solar cells grown on PSS were nearly identical to those of conventional devices. The enhanced performance is primarily due to improvements in the crystalline quality of the epitaxial layers, reducing the trapping of photogenerated electrons and holes by nonradiative recombination centers in MQW, with a corresponding increase in the transport efficiency of the carriers outside the device. (C) 2011 American Institute of Physics. [doi:10.1063/1.3605244]